The present invention relates to a laser patterning apparatus and method.
Photolithography is a well-known technique for producing patterns in thin films formed on substrates. This technique is convenient and advantageous, having regard to the desirability of removing portions of the thin film to be processed without causing damage to the underlying surface. However, a somewhat large number of steps is necessary for completing the patterning procedure in accordance with this method. Namely, after forming the thin film to be treated on a substrate, a photoresist film is formed and patterned, then the thin film is subjected to the action of an etchant with the patterned photoresist film used as a mask, and then the photoresist film is removed.
Laser scribing techniques are well known in the art and provide a low cost patterning method capable of operation at high speed. The YAG laser (IR light, 1.06 microns) is a representative laser which has been generally used for this purpose. Since the optical energy of this laser is only 1.23 eV, however, tin oxide, indium oxide (or ITO), ZnO and other materials having optical energy gaps of about 3 to 4 eV are not effectively processed by the YAG laser. Since transparent conductive oxide (CTO) films are generally made of this class of materials, the inability of YAG lasers to scribe such materials is a significant disadvantage.
The applicant has proposed the use of eximer lasers in order to emit pulsed laser beams for performing the laser scribing of transparent conductive films. The wavelength of the excimer laser beams is notgreater than 400 nm, equivalent to photon energies higher than 3.1 eV. With such an excimer laser, patterning can be performed by moving and positioning the laser beams relative to a surface to be patterned, and projecting a laser beam on the surface. For example, when a plurality of parallel grooves is formed, a substrate to be patterned is moved to an appropriate position relative to the laser beam projection position and irradiated with a flat laser beam, and this procedure is repeated in order to form parallel grooves. There is a significant disadvantage in this process. It must be repeated to move and stop the substrate relative to the laser projection position. This makes it difficult to make short the process time required for patterning. Particularly, the projection of a laser beam can not be done just after the stop of the substrate at a proper position. Rather, there has to wait a certain time between the projection and the stop of the substrate in order to avoid the influence of vibrations taking place just after the stop.